From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4DDE6C2BB48 for ; Sat, 5 Dec 2020 00:42:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2A35C22D71 for ; Sat, 5 Dec 2020 00:42:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730995AbgLEAl6 (ORCPT ); Fri, 4 Dec 2020 19:41:58 -0500 Received: from mail.kernel.org ([198.145.29.99]:48806 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726151AbgLEAll (ORCPT ); Fri, 4 Dec 2020 19:41:41 -0500 From: paulmck@kernel.org Authentication-Results: mail.kernel.org; dkim=permerror (bad message/signature format) To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, "Paul E. McKenney" , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , linux-mm@kvack.org, Andrii Nakryiko Subject: [PATCH sl-b 3/6] rcu: Make call_rcu() print allocation address of double-freed callback Date: Fri, 4 Dec 2020 16:40:54 -0800 Message-Id: <20201205004057.32199-3-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20201205004022.GA31166@paulmck-ThinkPad-P72> References: <20201205004022.GA31166@paulmck-ThinkPad-P72> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" The debug-object double-free checks in __call_rcu() print out the RCU callback function, which is usually sufficient to track down the double free. However, all uses of things like queue_rcu_work() will have the same RCU callback function (rcu_work_rcufn() in this case), so a diagnostic message for a double queue_rcu_work() needs more than just the callback function. This commit therefore prints the last allocation address of the double-freed callback when the callback is slab-allocated and sufficient debugging is enabled. It uses the shiny new kmem_last_alloc() and kmem_last_alloc_errstring() functions for this purpose. Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Andrew Morton Cc: Cc: Andrii Nakryiko Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index b6c9c49..788a072 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2957,6 +2957,8 @@ static void check_cb_ovld(struct rcu_data *rdp) static void __call_rcu(struct rcu_head *head, rcu_callback_t func) { + void *allocaddr; + const char *allocerr; unsigned long flags; struct rcu_data *rdp; bool was_alldone; @@ -2970,8 +2972,14 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func) * Use rcu:rcu_callback trace event to find the previous * time callback was passed to __call_rcu(). */ - WARN_ONCE(1, "__call_rcu(): Double-freed CB %p->%pS()!!!\n", - head, head->func); + allocaddr = kmem_last_alloc(head); + allocerr = kmem_last_alloc_errstring(allocaddr); + if (allocerr) + WARN_ONCE(1, "__call_rcu(): Double-freed CB %p->%pS()!!! (%s)\n", + head, head->func, allocerr); + else + WARN_ONCE(1, "__call_rcu(): Double-freed CB %p->%pS()!!! (Allocated at %pS)\n", + head, head->func, allocaddr); WRITE_ONCE(head->func, rcu_leak_callback); return; } -- 2.9.5